1. Field of the Invention
This invention relates to a radiation image readout apparatus for use in a radiation image recording and reproducing system. This invention particularly relates to a radiation image read-out apparatus which is adapted to installation in a small floor space.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. Nos. 4,258,264, 4,276,473, 4,315,318 and 4,387,428 and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet) is first exposed to a radiation passing through a object such as the human body to have a radiation image of the object stored thereon, and is then scanned with stimulating rays such as a laser beam which cause it to emit light in proportion to the stored radiation energy. The light emitted by the stimulable phosphor sheet upon stimulation thereof is photoelectrically detected and converted to an electric image signal, and the radiation image of the object is reproduced as a visible image by use of the image signal on a recording material such as a photographic film, a display device such as a cathode ray tube (CRT), or the like.
In the aforesaid radiation image recording and reproducing system, the stimulable phosphor sheet is used to temporarily store a radiation image until the sheet is scanned with stimulating rays to read out the radiation image. Therefore, after the radiation image is read out from the stimulable phosphor sheet, radiation energy remaining thereon should be erased to reuse the sheet.
For satisfying this requirement, it has been proposed to provide a radiation image read-out apparatus with a read-out section for reading out an image stored on a stimulable phosphor sheet, and an erasing section for erasing radiation energy remaining on the sheet.
The proposed radiation image read-out apparatus is provided with the image read-out section, the erasing section, a stimulable phosphor sheet feeding section for holding a cassette which houses therein a single image-recorded stimulable phosphor sheet carrying a radiation image stored thereon by use of an external image recording apparatus or a magazine which houses a plurality of the image-recorded stimulable phosphor sheets, and feeding out the image-recorded stimulable phosphor sheet from the cassette or the magazine, and a stimulable phosphor sheet housing section for holding a cassette or a tray for housing therein an erased reusable stimulable phosphor sheet on which image read-out and erasing have been finished. The stimulable phosphor sheet taken out of the stimulable phosphor sheet feeding section is conveyed to the image read-out section, the erasing section, and the stimulable phosphor sheet housing section in this sequence by a stimulable phosphor sheet conveyance means. As for the conveyance paths of the stimulable phosphor sheet conveyance means, the conveyance path from the stimulable phosphor sheet feeding section to the image read-out section, the conveyance path from the image read-out section to the erasing section, and the conveyance path from the erasing section to the stimulable phosphor sheet housing section are formed independently of one another.
In recent years, it is required to make small the aforesaid radiation image recording and reproducing system as whole, and to make the aforesaid radiation image read-out apparatus as compact as possible for this purpose. Particularly, if the bottom area of the radiation image read-out apparatus could be made small, it would become possible to decrease the space required for the installation of the read-out apparatus. However, with the conventional read-out apparatus wherein a plurality of the conveyance paths of the stimulable phosphor sheet conveyance means are formed independently of one another, the stimulable phosphor sheet feeding section, the image read-out section, the erasing section, and the stimulable phosphor sheet housing section must be put side by side on the conveyance paths, the width of the read-out apparatus becomes large, and the bottom area of the read-out apparatus cannot be decreased so much.